The vast hydrokinetic and potential energy in the swells of oceans, great lakes, and other large bodies of water, particularly prevalent at temperate and higher latitudes, has long been recognized as a potential, eventual source of abundant, renewable, and relatively very clean power for the future. In comparison to other “green” sources of energy humankind needs to exploit for power, particular features of ocean wave energy hold special promise. Unlike solar energy, it is available around the clock rather than diurnally. It persists longer than wind, and sometimes conveniently travels from points of generation toward the shore where population centers often are concentrated. It arises in the medium which covers three quarters of the globe, and even has the potential for enhancing the habit of life forms that dwell where it would be deployed without displacing human populations or competing land uses. Conflicting, incompatible, and prior private and sovereign claims on this resource are fewer than in the case of land based alternatives.
The predominant form of renewable oceanic energy by a wide margin resides in surface swells and waves over deep water especially to the lee of wide reaches and principally is found at temperate and greater latitudes both north and south. Energy in this form has already undergone a double conversion from solar to wind to wave. Other very significant and potentially harvestable sources of power certainly are present in bodies of water but which do not pertain to the present invention include tides, currents, temperature differentials, waves breaking on shore, and gravity water flow over land (e.g. hydroelectric dams). Well over two thirds of the energy is lost as swells move from deep to shallow water, hence the present invention is primarily intended for deep water deployment. The velocity of a deep-water ocean wave is proportional to its period, and waves of different period interact. The consequence of this dispersion is that faster moving waves can catch up and may combine with slower moving preceding shorter waves not always moving in exactly the same direction, with results both dangerous and difficult to predict. While the physics of an ideal wave is well described and calculable, an actual sea state is complexly multi-factored. Short time prediction of the direction and crest height of on-coming waves is a critical problem in the field of wave energy, but one far from fully solved. Mathematically, cyclical models, dynamic harmonic regression, auto-regressive models, and neural networks have all been brought to bear. It has been recognized in the field that a definitive solution, which so far has proven elusive, could be greatly beneficial to the development of effective Wave Energy Converters that would be economically viable.
Devices meant to reap power where energy abounds in open water had better be able stand up to and fend off—and/or duck—the punches Neptune can deal out. Severe conditions can unleash forces several magnitudes greater than normally prevail. In very high seas even water without whitecaps can pile up upon encountering obstacles in its path, and then sweep over like a breached dam at very high speeds. White water breakers can dump tons of water over objects in their way. Masses of water can rise over and come hammering down atop moored vessels. While adjectives like “gigantic”, “towering”, “immense” or “battering” commonly found in descriptions of waves in very high seas point to the power and uncertain duration of waves, historically words like “angry”, “treacherous”, “capricious”, “chaotic”, “tricky”, “rogue”, “constantly changing” and “freak” also occur frequently in this context, and testify to other problematic and difficult-to-model qualities of the ocean wave dynamic: the randomness, unpredictability, and frequency of anomalous, powerful occurrences at sea. Wave activity in roiling seas has required mariners from time immemorial to “expect the unexpected”, and gives vivid testimony to stochastic and nonlinear aspects of the complex hydrodynamics of the open water wave system. Marine design has been more an art and craft than a science for most of humanity's long sea-faring experience and largely remains so even up to today, another indication of the complexity of a still imperfectly understood natural environment.
The wave energy theoretically available for extraction by a floating apparatus is directly proportional to the area, and hence to the square of the radius, of the apparatus under which the swells pass. The great bulk of this energy resides in a thin layer at and just below the surface. These two monumental physical facts—the sporadically immense fits of violence unleashed in the oceanic environment and the superficial location of the mother lode of energy hopefully there to be mined—have loomed very large in the development of prior art in devising buoyant apparatus for converting this energy to useful power. By definition a buoyant apparatus is exposed to the teeth of the forces present at the surface. The recurrent question facing innovators in the field has been what shape and configuration of buoyant platform can best withstand the tremendous forces which it will have to face sooner or later and yet still effectively perform the desired function of converting energy to usable power. Many answers have been proffered, and even a quick survey of the main ones would be completely beyond our scope here, but the following general observations constitute essential background for the present invention.
One approach found in prior art employs a vertical configuration so as to minimize exposure of the apparatus' most buoyant components at the waterline. This has given rise to the branch of field concerned with point source solutions, with heavier parts of the apparatus located safely below—rigidly affixed to the sea bottom, a submerged segment tightly tethered to the buoyant component directly above, use of a “reactive mass” sunken underwater instead of a direct connection to the sea floor, and so forth. The relative calmness of the depths is a safe harbor for the lower part of the apparatus, in vertical counterpoint to the rising and falling of buoyant components overhead. Given drift due to wind, currents, and wash effects from piled up water breaking as waves, maintaining proper vertical alignment is a recurrent, daunting challenge when it comes to this vertical approach. A variation in the point sources branch of the science gives rise to the internal-external concentric collocation of buoyant and non-buoyant members in the manner of cylinder and piston, where the buoyant or heavier-than-water element may be either member, and there have been many inventions on this principle. Another problem is that cancelling harmonics can produce listless response in active waves of the wrong wavelength. However, the buoyant components of such vertically configured apparatus have had the benefit of borrowing from tried and true forms for navigational buoys developed over the last millennium. Many centuries of experience with navigational buoys have proven the worth of the vertically oriented shapes (barrel, nun, spar) that survive best under these worst-case conditions: all provide a primary axis not parallel to—but rather perpendicular to—the surface, with the bulk of the buoys' mass safely stowed below the waterline. However, considerable build up in terms of carrying capacity above waterline has shown to be quite acceptable provided aerodynamics and hydrodynamics that do not expose excessively broad, flat surfaces to the wind and waves.
An alternative branch of the field has taken a distinctly horizontal approach—specifying buoyant apparatus capable of lying across the surface in all conditions. Thus the art has seen the development of massively constructed, smooth bodied, segmented apparatus intended to ride out the extreme conditions fundamentally in same horizontal orientation as surface vessels. Probably the best known and tested exemplar features four linearly arranged segments the length size of light rail cars (each approximately 105 fee [32 meters] long) and cigar-shaped like surfaced submarines riding very low to the water, and linked end to end so as to snake in the troughs among swells as well as ride up and down in swells. The resulting mechanical work is used to drive hydraulic turbines running electric generators. Most ingeniously, the design incorporates innovations in confine the relative motion between segments in two not quite perpendicular planes, and by selectively switching the between the operating planes, to some extent the apparatus can be tuned to the prevailing conditions, either for increasing output or for reducing stress in extreme conditions.
In the branch of the field concerning energy buoys extending horizontally over the surface, inevitably there is a penalty to massive construction that is paid in terms of reduced efficiency under the less severe conditions which are present most of the time. It is only an object of trivial mass which “floats like a cork”. The inertia from their greater mass causes heavier buoys to rise and fall somewhat out of phase with the swells lifting them. Inertia and momentum causes them to overshoot the waves in which they rise and fall both on the way up and on the way down. On the one hand, segments of fixed length long enough to efficiently convert the power of swells in “well-organized” seas may plow through or float listlessly in choppy or chaotic seas converting little of the abundantly available short wave length energy to useful power. On the other hand, segments of fixed length short enough to function effectively in choppy, wind whipped conditions are ill-suited to tap the energy of powerful swells of longer amplitude and wavelengths. Segments meant to ride parallel to the wave surface needs must be massively constructed to survive the most violent conditions. The bridge design engineer's greatest nightmare—additive harmonics capable of leading to complete disintegration—can also disturb the sleep of the innovators in realm of horizontally floating articulating platforms for harnessing oceanic wave energy.